1. Field of the Invention
The invention relates to the controlled alteration of the lift/drag ratio of powered aircraft and more particularly to a selectively integrated throttle and spoiler control which enable the pilot of a powered aircraft to selectively modulate the aircraft's descent flight path under a wide range of power conditions.
It is a well known fact that a substantial percentage of general aviation accidents occur in the landing phase of flight. During landing the pilot's task is critical and a high degree of skill must be present to properly approach the runway, flare, touchdown, roll out and occasionally go-around with safety and within the prescribed landing zone. On approach air speed must be controlled within limits that avoid fast settling or stall and yet be slow enough to prevent improper flare or float. After touchdown the craft should be decelerated quickly for proper braking or taxi. In the event of go-around, air speed and flight path must be controlled to assure proper lift and stable flight conditions.
Enroute, ie., cross country air traffic control is also becoming more complex. As a result rapid descents from flight levels are more frequently required, even with general aviation aircraft. These descents usually require large power reductions and slower speed. This can jeopardize cabin pressurization, engine operation and orderly traffic flow.
Modulation of craft lift/drag ratio through the use of spoilers and/or dive brakes has been used on sail planes to provide rapid descent and increase the pilots landing skill. Jet transports use spoilers to reduce ground speed and landing roll upon undercarriage contact with the runway. In addition, there have been prior art attempts to develop spoiler and dive brake application to general aircraft, however, they have not been generally well received. To date not one general aviation air frame manufacturer has incorporated a lift/drag modulation device in the equipment produced. The added cost to original equipment manufacture would, of course, be a partial explanation. It may also be true that the prior art attempts did not possess the simplicity, efficiency and reliability to impress the general aviation industry.
2. Description of Prior Art
One effort to develop lift/drag modulation equipment for general aircraft is described in U.S. Pat. No. 3,850,388, dated Nov. 26, 1974. This patent teaches the integrated control of both an aircraft power throttle and a device for selective operation of lift/drag alteration equipment such as dive brakes and spoilers. A pair of pilot operated levers are provided which are physically adjacent each other. One lever is a throttle lever; the other lever controls the lift/drag equipment. The levers are integrated in the sense that only limited independent operation of the lift/drag operating lever is permitted and then only with a pilot felt resistive force which sensually notifies the pilot of such independent lever operation. During normal throttle down for conventional landing, the throttle lever and lift/drag lever are moved concurrently so that the spoilers and dive brakes are gradually extended as the power is reduced. This gradually increases the angle of steepness of the landing guide path. In the event full power is required, as during go-around, movement of either lever to forward position applies full engine power and concurrently deactivates the spoiler and dive brake equipment. Of course, because of the physical juxtaposition of the levers, both of them may be hand moved concurrently to forward position. The limited movement of the lift/drag lever relative to the throttle lever will provide limited special control situations for a pilot with a proper level of skill.
Another prior art aircraft throttle-spoiler actuator is U.S. Pat. No. 3,774,869, dated Nov. 27, 1973. The teaching of this patent suggests a single manually operated lever which is connected to a linkage and cam mechanism whereby throttle movement to an idle or neutral position as, for example, during landing simultaneously deploys a spoiler and dive brake thereby increasing descent rate. After full spoiler deployment, continued rearward movement of the throttle lever slightly increases engine power for taxi. Rapid forward movement of the throttle lever concurrently retracts the spoiler and brake and applies full engine power. A review of this patent will disclose what appears to be a rather complicated cam and linkage arrangement.